Method and apparatus for dynamically changing the preamble length of a burst communication

Abstract

Preamble length of burst communication signals dynamically changed to compensate in changes to linear distortion of a communication channel. Pre-equalization coefficients are provided to network element which pre-equalize communications with the CMTS. Long preamble lengths are used for a select few communications while short preamble lengths are used for the rest of the communication signals. When change in distortion characteristics is detected, a station maintenance is performed on the affected network element and new pre-equalization coefficients are determined and provided to the network element. Alternatively, all communications may be provided with long preamble lengths and communications may continue while the CMTS determines new pre-equalization coefficients.

1. An apparatus for communicating with network elements comprising:
 a transmission unit capable of transmitting signals to network elements; 
 a receiver unit capable of receiving signals from the network elements; 
 an equalizer unit configured to determine a change in distortion characteristics of the network in an affected network element's communication; and 
 a microprocessor configured to adjust the length of preambles associated with a signal to be transmitted by the network elements to provide preambles of a first length to a first group of communication signals to be transmitted by the network elements and to provide preambles of a second length to a second group of communication signals to be transmitted by the network elements, 
 wherein the first length is longer than the second length, and if the distortion characteristics have not changed, providing preambles of a first length to a first group of communication signals to be transmitted by the network elements and providing preambles of a second length to a second group of communication signals to be transmitted by the network elements. 
 
     
     
       2. The apparatus of  claim 1 , wherein the first group of communication signals include Initial Maintenance (IM) and Station Maintenance (SM) burst messages. 
     
     
       3. The apparatus of  claim 1 , wherein the first group of communication signals includes IM burst messages. 
     
     
       4. The apparatus of  claim 1 , wherein the microprocessor is configured to instruct a SM session to be scheduled for the affected network element if a change in distortion characteristics is detected. 
     
     
       5. The apparatus of  claim 4 , wherein the equalizer unit is further configured to determine pre-equalization coefficients during an SM session and the microprocessor is configured to instruct transmission of the pre-equalization coefficients to the affected network element. 
     
     
       6. The apparatus of  claim 4 , wherein the microprocessor is configured to instruct holding data grants to the affected network element during an SM session. 
     
     
       7. The apparatus of  claim 1 , wherein the microprocessor is configured to provide preambles of a first length to all communication signals to be transmitted by the affected network element. 
     
     
       8. The apparatus of  claim 7 , wherein the equalizer unit is further configured to determine pre-equalization coefficients from the preamble of a first length and the microprocessor is configured to instruct transmission of the pre-equalization coefficients to the affected network element. 
     
     
       9. The apparatus of  claim 1 , wherein a change in distortion characteristics is determined by monitoring energy in taps of the equalizer coefficients. 
     
     
       10. The apparatus of  claim 1 , wherein a change in distortion characteristics is determined by monitoring a change in a modulation error ratio. 
     
     
       11. The apparatus of  claim 1 , wherein a change in distortion characteristics is determined by monitoring a microreflection metric. 
     
     
       12. A method of communicating with network elements which perform pre-equalization using pre-equalization coefficients comprising the steps of:
 determining if the distortion characteristics of a network associated with an affected network element have changed; and 
 if the distortion characteristics have not changed, providing preambles of a first length to a first group of communication signals to be transmitted by the network elements and providing preambles of a second length to a second group of communication signals to be transmitted by the network elements, 
 further comprising the step of instructing a SM to be scheduled for the affected network element if a change in distortion characteristics is detected, 
 wherein the first length is longer than the second length. 
 
     
     
       13. The method of  claim 12 , wherein the first group of communication signals includes IM and SM burst messages. 
     
     
       14. The method of  claim 12 , wherein the first group of communication signals includes IM burst messages. 
     
     
       15. The method of  claim 12 , further including the steps of determining new pre-equalization coefficients during an SM session and providing the new pre-equalization coefficients to the affected network element. 
     
     
       16. The method of  claim 12 , further comprising the step of holding data grants to the affected network element during an SM session. 
     
     
       17. The method of  claim 12 , further comprising the step of providing preambles of a first length to all communication signals to be transmitted by the affected network element if a change in distortion characteristics is detected, and the pre-equalization coefficients are determined from the preambles of a first length. 
     
     
       18. The method of  claim 12 , wherein a change in distortion characteristics is determined by monitoring energy in taps of equalizer coefficients. 
     
     
       19. The method of  claim 12 , wherein a change in distortion characteristics is determined by monitoring a change in a modulation error ratio. 
     
     
       20. The method of  claim 12 , wherein a change in distortion characteristics is determined by monitoring a microreflection metric. 
     
     
       21. A computer readable medium containing instructions for a computer to perform a method of communicating with network elements which perform pre-equalization using pre-equalization coefficients comprising the steps of:
 determining if the distortion characteristics of a network associated with an affected network element have changed; and 
 if the distortion characteristics have not changed, providing preambles of a first length to a first group of communication signals to be transmitted by the network elements and providing preambles of a second length to a second group of communication signals to be transmitted by the network elements, 
 further comprising the step of instructing a SM to be scheduled for the affected network element if a change in distortion characteristics is detected, 
 wherein the first length is longer than the second length. 
 
     
     
       22. The computer readable medium of  claim 21 , wherein the first group of communication signals includes IM and SM burst messages. 
     
     
       23. The computer readable medium of  claim 21 , wherein the first group of communication signals includes IM burst messages. 
     
     
       24. The computer readable medium of  claim 21 , further including the steps of determining new pre-equalization coefficients during an SM session and providing the new pre-equalization coefficients to the affected network element. 
     
     
       25. The computer readable medium of  claim 21 , further comprising the step of holding data grants to the affected network element during an SM session. 
     
     
       26. The computer readable medium of  claim 21 , further comprising instruction to perform the step of providing preambles of a first length to all communication signals to be transmitted by the affected network element if a change in distortion characteristics is detected, and the pre-equalization coefficients are determined from the preamble of a first length. 
     
     
       27. The computer readable medium of  claim 21 , wherein a change in distortion characteristics is determined by monitoring energy in taps of equalizer coefficients. 
     
     
       28. The computer readable medium of  claim 21 , wherein a change in distortion characteristics is determined by monitoring a change in a modulation error ratio. 
     
     
       29. The computer readable medium of  claim 21 , wherein a change in distortion characteristics is determined by monitoring a microreflection metric.